The present invention relates to a method for producing a spectacle lens and a lens processing system, and particularly to a method for producing a spectacle lens, which method is improved in production yield, and a lens processing system used for the production method.
Spectacles have been fabricated in spectacle shops as follows: namely, circular spectacle lens have been subjected to edge cutting work called xe2x80x9cedgingxe2x80x9d in matching with inner shapes of openings of a spectacle frame selected by a user, and the edged lenses thus obtained have been fitted in the openings of the spectacle frame.
In recent years, however, because of the lack of the number of laborers skilled in works of edging and inserting the edged lenses in spectacle frames and employed in spectacle shops, there have been strong demands for lens makers to process lenses until edging and deliver the edged lenses to retail shops.
On the other hand, plastic lenses having a merit easier to be dyed are superior in fashion and light-shield characteristics to glass lenses, and from this viewpoint, there have been strong demands for dyeing of plastic spectacle lens. In particular, demands for gradation dyeing of a lens have become strong. The gradation dyeing is performed by gradually reducing a dyeing density generally from a densely dyed upper half of a lens to a non-dyed bottom side thereof.
Lenses to be finished until the dyeing work and edging are customized, and in such customization, the number of production steps becomes larger than that of ordinary production steps.
In customization of lenses required to be processed until the dyeing work and edging, recipe information of the lenses is previously supplied from a retail shop. The recipe Information includes not only information on a dioptric power and an astigmatism of each of the lenses, but also spectacle frame information indicating shapes of inner peripheral edges of openings of the spectacle frame required for edging, and dyeing specification information on a color tone of dyeing and on the fact whether or not the dying is gradation dying.
On the lens production side, the recipe information is converted into information required for production of spectacle lens. To be more specific, a work instruction sheet and a work confirmation drawing are printed for each of the lenses. Various work instructions are written on the work instruction sheet. A full-size circular lens closing line and a full-size edging line indicating the contour of an edged lens are written, together with a reference line, on the work confirmation drawing. The work instruction sheet and the work confirmation drawing are shifted from one to another step together with a lens to be processed.
FIG. 5 shows steps of producing a customized plastic lens required to be finished until the dyeing and edging steps. The process starts with a lens material polymerization step at which a monomer as a lens material is poured in a mold typically a glass mold, followed by polymerization, to obtain each lens having a specific dioptric power. If the lens is of a multi-focal type, concealed marks for determining a fitting point are transferred from the mold onto a surface of the lens thus obtained.
A polishing step includes polishing work for imparting desired optical characteristics to the lens of a kind impossible to be stocked, such as a lens having a dioptric power out of a usual range or a progressive multi-focal lens, and thinning work for making the lens as thin as possible in matching to the shape of a spectacle frame with its dioptric power kept at a specific value. It is dependent on the kind of a spectacle lens whether or not the polishing step should be carried out.
A dyeing step is carried out for coloring the lens into a specific color. It is dependent on the kind of a lens whether or not the dyeing should be carried out. At the dyeing step, which is carried out on the basis of dyeing specification information, a lens is dipped in a solvent in which a dye has been dissolved, whereby the surface of the lens is colored with the dye.
At a hard coat formation step, the lens is dipped in a hard coat solution, followed by drawing up and drying, to form a hard coat having a good abrasion resistance on the surface of the lens.
At anti-reflection coating formation step, a multi-layer film of, typically, inorganic oxide layers are deposited on the lens by vacuum vapor-deposition, to form anti-reflection coating on the lens.
The lens processed until the above-described steps have been taken as a finished product; however, recently, the lens has been often required to be further processed until the edging step. The edging step is carried out by cutting off the outer peripheral edge of the lens into a shape equivalent to a shape of an inner peripheral edge of an opening, in which the lens is to be fitted, of spectacles on the basis of spectacle frame information supplied from a retail shop.
The lens is inspected at each of the above-described steps, followed by final inspection, to be finished. The spectacle lens thus finished is supplied to a retail shop.
With respect to the above-described conventional lens production steps, along with the increased demand for a lens maker to process lenses until the edging, it has been required to review the conventional production steps.
For a lens processed until the anti-reflection coating formation step before the edging step and supplied as a finished product to a retail shop, a desired appearance quality must be guaranteed over the entire lens except for only a region from the outermost periphery to a line positioned inwardly therefrom by about 1 mm. Here, appearance defects of a lens may include the entrapment of foreign matters, polymerization strain, and bubbles at the lens material polymerization step, the entrapment of foreign matters and solution sag at the outer peripheral portion at the hard coat formation step, uneven dyeing at the dyeing step, and partial penetration at the anti-reflection coating formation step. That is to say, these appearance defects must be perfectly eliminated over the entire lens.
For a lens processed until the anti-reflection coating formation work, which lens is to be further subjected to the edging in a lens maker, since a region of the lens outside the shape of a edged lens is to be cut off, the appearance quality in the region is not required to be guaranteed. Even for such a lens, however, the appearance quality has been guaranteed over the entire lens just as the above-described lens not subjected to edging, with a result that the production yield of the lenses of this type has been degraded.
On the other hand, gradation dyeing at the dyeing step is carried out by dipping the upper side of a lens in a dye solution and moving it up and down in the dye solution, to form gradation of dyeing. Accordingly, upon gradation dyeing, it is required to dip a lens in a dye solution in a state in which the vertical direction of the lens is accurately set. To meet this requirement, an operator impresses the principal meridian direction and horizontal direction determined from a concealed mark or an astigmatism axis on the lens by using a diamond pen or the like, and sets the lens such that the impressed position is aligned to a specific position of a dyeing jig. As a result, there occur problems that the dyeing work is complicated, the automation of the dyeing step is obstructed, and an error of dyeing position may occur due to a working mistake or a variation in setting position between operators.
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a method for producing a spectacle lens, which is capable of carrying out appearance inspection only for a portion required for guarantee of an appearance quality of the lens, and further reducing the dyeing work, allowing automation of dyeing, and enhancing the dyeing accuracy at a dyeing step.
Another object of the present invention is to provide a lens processing system used for the method for producing a spectacle lens.
As a result of examination to achieve the above object, the present inventor has paid attention on the fact that a spectacle lens is cut off except for a region finally remaining after edging (hereinafter, referred to as xe2x80x9cedged lens regionxe2x80x9d), and found that if information on the shape of a edged lens to be fitted in an opening of a spectacle frame is given, various kinds of production information required for production of the lens can be depicted in the region to be cut off by the edging.
If an edging mark indicating an edged lens region is depicted as production information of a lens, the quality of only a region inside the edging mark may be guaranteed, and accordingly, even if defects are observed in a region outside the edging mark, these defects are negligible. If such an edging mark is not depicted, a region whose quality should be guaranteed is indefinite, and accordingly, the quality of the entire lens must be guaranteed, so that the production yield is degraded because of over-quality. On the other hand, if reference position marks are depicted as production information of a lens before dyeing, mark impressing work for alignment of the lens to a jig for gradation dyeing can be omitted, so that it is possible to automate a dyeing step and to improve the dyeing accuracy.
The production information such as the edging mark and reference position marks depicted on a lens cannot be erased; however, if the production information is depicted on a region of the lens, to be cut off by the edging, the appearance of the finished lens obtained by removing the region is not affected by the production information.
The edging mark may be configured as an edging line slightly larger than and similar to a shape of a peripheral edge of the edged lens. The edging line thus depicted, which can indicate the edged lens region, does not remain in the finished product because it is depicted in the region to be cut off by the edging.
The present inventor has also found that a lens processing system, which has a reference position detecting apparatus for detecting reference positions by typically detecting concealed marks impressed on a lens and a marking apparatus for depicting specific production information at a specific position of the lens on the basis of the reference position information, is effective for depiction of production information such as edging mark on the lens.